1. Field of the Invention
The present invention generally relates to a method for driving a display, and more particularly, to a method for driving a display using a color sequential method.
2. Description of Related Art
Along with the development of photoelectric and semiconductor technology, the flat panel display technology is also being rapidly developed and has made significant progress. Among various displays, a liquid crystal display (LCD) has played a major role in the mainstream display market due to advantages of low power consumption, no radiation and low electromagnetic interference thereof. An LCD includes an LCD panel and a backlight module. The backlight module provides the LCD panel with a planar light source so as to make an LCD panel have display function.
The backlight module of a conventional LCD is a white light source, which emits white light passing through color filters to serve as a backlight source of the LCD panel. At each pixel positioned on the LCD panel, three color filters including a red filter, a green filter and a blue filter are disposed. Thus, this arrangement would incur higher cost and causes a color-blending problem at all boundaries between any two of the color filters. Although disposition of a black matrix at any adjacent position between the red, green and blue filters can decrease the color-blending problem, the solution would make the optical transmittance of the color filters poor.
Based on the above-mentioned problems, a display-driving technique by using a control circuit in association with a color sequential method was developed, wherein the display-driving technique uses the light-emitting diodes (LED) to replace the traditional white backlight source. Instead of the prior art where color filters are used to make any three sub-pixels localized within a tiny dimension (less than a viewing-angle resolution of human eyes) color-blended, the technique uses an LED backlight source to sequentially accomplish color-blending (within the duration of persistence of human eye's vision, three color images, i.e. red, green and blue color images, are quickly switched to achieve color-blending effect). It can be seen that the display technique does not need a color filter and promotes the optical transmittance of the display panel.
Although the display-driving technique by using a control circuit in association with the color sequential method is able to promote the optical transmittance of the display panel and effectively reduce the flaw in a display using color filters. However new problems, for example a color breakup (CBU) problem associated with the technique have been identified. Due to human eye's random saccades or the instinct of pursuing the object on screen frame, in terms of visual perception, the color fields corresponding to each color of an object on a frame do not fall onto a same point of human eye's retina, therefore, a color breakup occurs at edges of an object on a screen frame.
FIG. 1A is a diagram showing a color breakup phenomenon. Referring to FIG. 1A, to complete displaying a full-color frame by using the color sequential method in the prior art, a frame is completed by four sequentially displayed sub-frames with three colors, and the red sub-frame R, the green sub-frame G and the blue sub-frame B are quickly and sequentially displayed to produce a full-color image. Taking a white image W as an example, a white image 110 observed by a moving observing point would have a left edge with blue color (B) and a combination of blue color plus green color (B+G) and a right edge with red color (R) and a combination of red color plus green color (R+G), both of which are not desired edges with white color (W).
Based on the above-introduced background, some schemes to improve the color breakup were accordingly proposed. For example, the Taiwan patent publication No. 494686 proposes a scheme to perform image processing and dynamic compensation on a full-color frame by using motion-compensation, and to eliminate color breakup by predicting motions of an object on screen frame. Another scheme provides a display flowchart of a conventional driving method shown by FIG. 1B. According to the flowchart, a full-black frame is added between any two color-sequences; that is a black sub-frame is added after showing a red sub-frame R, a green sub-frame G and a blue sub-frame B so as to make a red sub-frame, a green sub-frame, a blue sub-frame and a black sub-frame display in sequentially cycling mode to reduce color breakup. Yet another scheme provides a display flowchart of a conventional driving method shown by FIG. 1C, wherein color-sequences are altered to reduce the human-eye effect. For example, a first full-color frame F1 is composed of three sub-frames sequentially arranged in the order of red (R), green (G) and blue (B), while the second full-color frame F2 is composed of three sub-frames sequentially arranged in the order of blue (B), red (R) and green (G).
However the above-described methods for driving a display targeting to reduce color breakup is not faultless. In terms of the scheme of compensating motion, the additional operations of image processing and dynamic compensation are required, in particular, it is hard to predict the motions of an object on the screen. In terms of the scheme of inserting black sub-frames or altering color-sequences, it is a limitation of the scheme that all the processing targets a whole frame, which helps to reduce the human eye's perception of color breakup to a limited extent only.